SNAPC4 is a critical component of the snRNA-activating protein complex (SNAPc), which regulates transcription of small nuclear RNA genes required for RNA processing 1. As a DNA-binding subunit of SNAPc, SNAPC4 recognizes the proximal sequence element in snRNA promoters and recruits transcription factors essential for both RNA polymerase II and III-dependent snRNA transcription 2. The protein's function is evolutionarily conserved across eukaryotes 2, and its activity is regulated through SUMOylation, which is necessary for proper SNAPc complex assembly and snRNA transcriptional activity 3. Bi-allelic SNAPC4 variants cause autosomal recessive neurodevelopmental disorder characterized by developmental regression, progressive spastic paraparesis, and oromotor dysfunction 1. Loss of SNAPC4 function leads to decreased snRNA expression and global dysregulation of alternative splicing, impairing the spliceosome's ability to process transcripts 1. Beyond neurological disease, genetic variants in SNAPC4 have been associated with ankylosing spondylitis susceptibility in multiple populations 45, and shared genetic overlap with inflammatory bowel disease and iridocyclitis 6. SNAPC4 dysfunction represents a previously unrecognized mechanism disrupting splicing-dependent cellular processes critical for neurological development and immune homeostasis.